A standard system design parameter for computer systems is that a loss of power for one cycle of the AC power input, e.g., about 17 milliseconds for a 60 hertz power supply, will not interrupt the operation of the system. In order to support this parameter, present power supplies often have large capacitors used to supply power to the system while the AC input is too low. Additionally, power supplies are designed with some amount of rating margin needed to handle worse-case loading conditions on the system. Loading conditions in real use are much lower and the higher loads are present only for a short duration.
Various systems are used to reduce power demand during critical power events, such as under power, thermal excursions, platform power constraints, network power constraints, and the like. However, there is currently no mechanism for throttling the power usage of peripheral component interface (PCI) devices when the need arises. PCI devices often consume as much as 15% of total power. Further, PCI and I/O power as a percentage of the total server power will grow as more high power devices like general purpose (GP) central processing units (CPUs), graphic processing units (GPUs), network based offload processors, and the like are installed in servers. If a platform includes a number of these higher power devices, the power consumption of these devices may constitute more than 50% of the total power required by the platform.
The same numbers are used throughout the disclosure and the figures to reference like components and features. Numbers in the 100 series refer to features originally found in FIG. 1; numbers in the 200 series refer to features originally found in FIG. 2; and so on.